JOHANNESBURG, South Africa -- The dramatic trial of Winnie Mandela on charges of kidnapping and assault ended its second week of testimony yesterday with defense lawyers attempting to shift the emphasis of the case to homosexuality.

Mrs. Mandela, the flamboyant wife of African National Congress

leader Nelson Mandela, and three co-defendants are charged with abducting three young men and a teen-age boy from a Methodist Church parsonage in late 1988. Mrs. Mandela's defense is that the four were taken to her home for protection from a minister who was sexually abusing them.

Two witnesses have testified already that they were not abused by the minister, but were severely beaten by Mrs. Mandela and her bodyguards in a storage house in her back yard. They said Mrs. Mandela slapped, punched and whipped them after listening to accusations that they had had sex with the white minister.

Mrs. Mandela's chief bodyguard has been convicted of murdering the teen-ager and sentenced to death.

A Methodist Church bishop testified Friday that church and community leaders conducted an investigation in 1989 and "unanimously ex

pressed confidence" in the Rev. Paul Verryn, who allowed homeless or troubled boys to stay at the Methodist house.

Bishop Peter Storey said Mr. Verryn had had "an absolutely unblemished record" when the charges of homosexuality surfaced.

The two key witnesses, Kenneth Kgase and Thabiso Mono, have told the court that Mr. Verryn typically shared a bed with one or two youths at the parsonage, which was often overcrowded with boys sleeping on sofas and on the floor.

The bishop said conditions in the township parsonage would not have been "acceptable in a good boarding school. . . . The impression I got is that whatever the shortage of accommodation, there was always room for one more."

Mrs. Mandela's lawyer, George Bizos, told the court that he would produce witnesses who would tell of being fondled by Mr. Verryn. When asked by the judge if the action was improper, Mr. Bizos responded, "My lord, it was completely improper."

The defense strategy seems to be to shift the focus from Mrs. Mandela to Mr. Verryn and to discredit the witnesses by suggesting that they are trying to protect the minister.

Justice Michael S. Stegmann will weigh the arguments. South Africa does not have jury trials.

The trial, which began Feb. 4, has sparked heated debate about the role of the African National Congress, an anti-apatheid organization in which Mrs. Mandela and her husband hold leadership positions. Mrs. Mandela is the ANC's director of social welfare.

Critics charge that some ANC officials are trying to portray the case as a political trial, although Mrs. Mandela is charged with common crimes. ANC leaders counter that Mrs. Mandela was tried and found guilty in the press even before the trial began.

Some have said the case is being used to hurt the anti-apartheid organization during its negotiations with the government on political reforms for the country.

When the trial began, ANC officials lined the benches in the small courtroom, but most have disappeared since testimony began about the alleged beatings at the Mandela home.

Even Mr. Mandela, who accompanied his wife to court every day at the beginning, did not attend most of the proceedings this week.